This invention relates to the field of power tools and in particular to the field of hand-held reciprocating saws.
Reciprocating saws are often used by tradesmen, such as carpenters, plumbers, and electricians for making rough cuts in wood or other hard materials. Manually sawing these materials would be a difficult and time consuming undertaking. Further, many applications require a saw to be used in a confined area where it would be even more difficult to move a saw blade manually back and forth. Consequently, reciprocating saws relieve the user from having to generate the reciprocating action of the saw blade. The motive force in a reciprocating saw is conventionally provided by a motor instead of by the user. The motor typically drives a drive assembly, which in turn reciprocates a saw blade or other tool.
Known reciprocating saws suffer from several drawbacks. In some known reciprocating saws, the motor, drive assembly, reciprocating shaft and blade are each longitudinally aligned along a common axis, creating a tool having a length at least as long as the combined longitudinal length of the motor, drive assembly and reciprocating shaft. This configuration causes the saw to be longer than necessary, which can render impossible, or at best complicate, some cuts to be performed in a limited space. A long saw is also generally awkward to use and unwieldy, and is difficult to store when not in use. Furthermore, the length of the saw can prevent the saw from balancing and standing upright on a flat surface such as a tradesman""s scaffolding, a ladder, or a retail shelf.
Furthermore, in some known reciprocating saws, the housing for the saw assembly is unnecessarily complicated and expensive. Openings in the housings of reciprocating saws to facilitate cooling the motor also allow saw dust and other debris to enter into the housing and contaminate the components within the housing. Thus, separately sealed gear box housings are used to enclose some of the working components of the saw, protecting them from debris.
One known arrangement, such as that disclosed in U.S. Pat. No. Re. 35,258, has a separate gear box outside of and attached to the exterior of the housing which surrounds the motor. Having the separate gear box attached to the exterior of the motor housing presents several drawbacks.
First, the exterior surface of the gear box can be expensive to manufacture. For aesthetic and comfort reasons, the external surfaces of the saw are generally smooth and polished. Since, with this design, the exterior surface of the gear box is also an external surface of the saw, at least a portion of the exterior surface is sometimes manufactured to be smooth. Manufacturing a smooth gear box can increase the cost of the saw.
Second, an insulating cover is sometimes required to be fitted around the exterior surface of the gear box in this design. The insulating cover can protect the user from electrical shock if a live electrical wire is cut with the saw. Also, since the gear box can become very hot during prolonged use of the saw, an insulating covering is sometimes necessary to insulate a user""s hands from the heat of the gear box. Applying an insulating covering to the gearbox, while potentially eliminating the cost of producing a smooth gear box, is nonetheless still an added expense.
Third, with the design of the ""258 patent, the external gear box must be securely attached to the exterior of the motor housing. This can add to the cost of manufacturing the saw.
Furthermore, reciprocating saws create vibration. U.S. Pat. No. Re. 35,258 attempts to address this problem. It discloses a reciprocating saw having a counterbalanced reciprocating mechanism. The counterbalance in the ""258 Patent purportedly uses the momentum of a counterbalance to reduce the vibration caused by the combined momentum of a reciprocating shaft and saw blade. While such a configuration may diminish undesirable vibration, it does not provide a configuration as compact and convenient as possible.
These and other drawbacks of known reciprocating saws are overcome by the invention as disclosed herein in conjunction with the preferred embodiments.
According to one embodiment of the invention, a reciprocating shaft and bearing combination for a reciprocating saw comprises a housing, a first pin fixed to the housing, and a reciprocating shaft assembly having a blade holder at a first end thereof for holding a saw blade. The reciprocating shaft assembly moves in a reciprocating motion relative to the first pin and parallel to an axis of motion. The reciprocating shaft assembly also has at least a first bore formed in a second end thereof opposite the first end, with the axis of the first bore being formed parallel to the axis of motion. A portion of the first pin is positioned inside the first bore such that the first pin supports the reciprocating shaft assembly as a bearing during its reciprocating motion.